In the context of the research proposal, a competitive PCR assay will be used to analyze the profiles of expression of the mRNAs encoding subunits of the GABA-A receptor during development (in vivo) and as cerebellar granule cells differentiate in vitro. This information will be correlated with a comparable in situ hybridization analysis during development in vivo. The hypothesis that cell type specific patterns of expression of the receptor subunit mRNAs are influenced by both heterologous and homologous receptor stimulation will be tested. In the context of, the mechanism by which this trans-synaptic regulation of GABA-A receptor subunit mRNAs occurs will be investigated.